The guidance says stagnant water presents optimal conditions for the growth of pathogens like Legionella. Stagnant water also changes water chemistry, which may increase corrosion and leaching of metals, including lead. “Turning on the water for immediate use after it has been stagnant can pose a risk to public health if not properly managed,” the guidance notes. “Additionally, turning on water after a prolonged period of non-use could disrupt pipe and plumbing scales to such an extent that microbial and chemical contaminants could be released into the water.”

Among the EPA’s recommended steps to maintain water quality while buildings/businesses are closed for building owners/managers are:

Review and understand the plumbing configuration and water usage in your building.